Field of the Invention
The invention relates to a cutting tool, particularly for use in a tool chuck of a machine tool, comprising a tool shaft with a center longitudinal axis and a tool head.
Description of Related Art
Cutting or machining tools such as, for example, milling tools or lathe tools, are constructed from multiple parts in some cases and usually comprise a tool shaft and a tool head connected thereto. The tool head in this case is used for the actual machining of workpieces, i.e. to remove material, and accordingly has at least one cutting edge or one cutting insert. The tool shaft, on the other hand, is normally formed for use in a tool chuck of the machine tool and frequently functions additionally as a type of extension so that the tool head can be positioned in the desired location, for example in a recess or borehole.
As a result of this, a cutting tool typically has an elongated shape and is additionally clamped on one side when ready for operation. Therefore, it behaves similar to a cantilever or bent bellows clamped on one side, the free end of which is subject to bending and torsional forces, when workpieces are machined.
When selecting suitable material for a cutting tool, care must be taken to ensure that the material can withstand the maximum possible bending and torsional forces and is additionally as nonsensitive as possible to impacts. This applies, for example, to so-called high-speed steels that are accordingly used frequently. The hardness of such types of high-speed steels is insufficient for an entire series of applications however, which is why in such cases it is preferable to use so-called carbides. In comparison to high-speed steels, carbides have increased hardness and accordingly enable machining also of workpieces made of harder materials with cutting tools made of carbide. In addition, the wear that occurs caused by abrasion is less with the corresponding carbides. However, as the hardness increases, typically the brittleness of a material also increases, which means that suitable carbides are relatively sensitive to impacts or vibrations.
In addition, brittle materials also have the problem of stress effects, because they do not plastically deform when reaching the elasticity limit but instead immediately fracture so to speak. This is particularly significant with so-called cutting system tools made of carbide. With a corresponding system tool, a tool change head made of carbide, for example a replaceable milling head, is screwed into a tool shaft under pretension. A carbide-carbide connection is critical due to the stresses.
In order to then obtain a cutting tool that is as wear-resistant as possible and also as nonsensitive to impacts, vibrations, and bending forces as possible, different materials are combined with one another and a corresponding cutting tool is designed so to speak from multiple parts. Thus, WO 0033994 A1 describes, for example, a cutting tool for use in a tool chuck of a machine tool having a tool shaft and a tool head, in which different metals having differing hardness and thus differing brittleness as well are used for producing the tool head and tool shaft. When producing the cutting tool, the tool head and the tool shaft are connected to one another, for example, through soldering, in which the ends of the tool shaft and the tool head soldered together have complementary-formed V-shaped profiles.
This design is also used in a similar form for cutting system tools, in which a coupling element or a connecting element made of a tool steel is inserted between the tool change head made of solid carbide and the tool shaft also made of solid carbide. The tool shaft and the coupling element in this case are bonded together through soldering, in which the ends of the tool shaft and the coupling element soldered together have complementary-formed V-shaped profiles. The tool change head is then screwed into the coupling element and no longer in the tool shaft.
The problem with cutting tools designed in this manner, however, is the fact that the corresponding solder connections will fracture under higher loads.